Process for breaking down foam



United States Patent 3,378,500 PRDCESS FOR BREAKING DOWN FOAM Carl Robert Sahlberg, 1 Ingentingsgatan, Solna, Sweden No Drawing. Filed Nov. 15, 1965, Ser. No. 507,646 Claims priority, application Sweden, Nov. 16, 1964, 13,807/ 64 5 Claims. (Cl. 252-321) ABSTRACT OF THE DISCLOSURE In the production of pulp from cellulcsic fibrous material by conventional aqueous alkaline methods, the process of breaking down foam which comprises separating same and bringing it into contact with an inorganic acid in liquid or gaseous form.

This invention relates to a process in the technique of producing pulp from cellulosic fibrous material by an aqueous alkaline process. When producing such a pulp, as e.g. when using the sodaor sulfate method or the alkaline sulfite method, intense foaming occurs, particularly when the pulp produced has a Roe-number above 4, eg when oxidizing the residual liquor and when washing the pulp, due to the soaps having been formed from resinous and fatty substances in the wood. The conventional soda and sulfate methods of producing pulp from cellulos-ic fibrous material are treated in greater detail in Othmers Encyclopedia of Chemical Technology (1953), Vol. 11 particularly pages 263-266 and details of the alkaline sulfite method may be found in US. Patent No. 3,046,182 to Tomlinson et al.

The foam so formed will be broken down if it is allowed to stand sufficiently long a period of time, and this breaking down may also be accelerated by means of mechanical devices. When the foam has obtained a certain stability and the amount of foam is great, there is nevertheless no possibility to break down all the foam with those mechanical devices.

This invention is directed to a process in which such disadvantages are eliminated and this invention comprises separating the foam and bringing the foam as separated in contact with an inorganic acid. This acid is preferably a strong acid, as e.g. a mineral acid, particularly sulfuric 3,378,500 Patented Apr. 16, 1968 acid or hydrochloric acid. If desired, it can also be a gas, e.g. sulfurdioxide. The expression inorganic acid is also intended to mean so called acid salts, as e.g. acid sodiumsulfate, which salts can be considered as a neutral salt plus acid. The acid can be used in concentrated or diluted form the diluents preferably being aqueous, as e.g. usually water.

The mechanism when using this process seems to be that the soap being present in the foam is broken down so that free resinous and fatty acids are formed the ability to foam being lost.

The acid can be sprayed to the foam from a pipe or supplied to the foam in a finely divided form (e.g. an atomized form) in another manner known per se when the foam has been separated from the foaming material, i.e. the residual liquor. Alternatively, the acid can be mixed with the foam in an ejector. It is also possible to mix the foam with the acid in a packed column so that the foam also in this case is treated separately.

What I claim is:

1. In a process for producing pulp from cellulosic fibrous material by an aqueous alkaline process in which intense foaming occurs due to the formation of soaps from resinous and fatty substances in said cellulosic fibrous material, the method which comprises separating said foam and contacting same with an inorganic acid in an amount suflicient to break down the foam to form free resinous and fatty acids.

2. The process according to claim 1 wherein said acid is supplied in form of a gas.

3. The process according to claim 2 wherein said gas is sulfur dioxide.

4. The process according to claim 1 wherein said acid is supplied in form of a dilute solution.

5. The process according to claim 4 wherein said acid is selected from the group consisting of sulfuric acid and hydrochloric acid.

References (Jited UNITED STATES PATENTS 2,317,139 4/ 1943 Frantz 25-2-321 2,622,107 12/1952 Mattson 252-321 X 2,668,150 2/1954 Luvisi 252-321 LEON D. ROSDOL, Primary Examiner.

R. D. LOVERING, Examiner. 

